Orthopedic fixation devices and methods thereof

ABSTRACT

Orthopedic fixation devices, assemblies, and methods for securing a spinal rod. The orthopedic fixation device may include a tulip head, a bone fastener, a rotatable saddle, and a threaded locking cap. The saddle may be insertable into the tulip head in an unlocked position with a rod seat offset relative to a rod slot of the tulip head. The saddle may be rotated into a locked position with the rod seat aligned with the rod slot such that a rod is positionable through the rod slot and into the rod seat. The threaded locking cap may secure the rod and bone fastener.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S. patentapplication Ser. No. 17/176,435 filed on Feb. 16, 2021 which isincorporate in its entirety herein.

FIELD OF THE INVENTION

The present application relates generally to orthopedic fixationdevices, and more particularly, bone fastener assemblies, for example,for spine surgery.

BACKGROUND OF THE INVENTION

Many types of spinal irregularities cause pain, limit range of motion,or injure the nervous system within the spinal column. Theseirregularities may result from, without limitations, trauma, tumor, discdegeneration, and disease. Often, these irregularities are treated byimmobilizing a portion of the spine. This treatment typically involvesaffixing one or more bone fasteners, such as screws, hooks, or clamps,to one or more vertebrae and connecting the bone fastener(s) to anelongate spinal rod that stabilizes members of the spine.

The bone fixation device may include a tulip head for coupling the bonefastener to the elongate spinal rod. A locking cap may be used to securethe elongate spinal rod in the tulip head. There exists a need forimproved functionality, strength, and/or ease of manufacturing of thebone fixation components.

SUMMARY OF THE INVENTION

To meet this and other needs, bone fastener devices, assemblies,implants, systems, and methods of treating spinal irregularities areprovided. The implant or assembly may include a tulip head with alocking cap for securing the spinal rod therein. The implant may beconfigured for use with a variety of screws, such as polyaxial,uniplanar, monoaxial, reduction, modular, etc. The bone fastener may beimplanted, for example, in open, semi-open, or percutaneous approachesto the posterior spine.

According to one embodiment, an orthopedic fixation assembly includes atulip head, a bone fastener, a saddle, and a locking cap. The tulip headmay include two arms defining a rod slot therebetween. The tulip headdefines a bore extending therethrough and a groove disposed about thebore. The bone fastener includes a screw head receivable in the tuliphead and a shaft configured for engaging bone. The saddle includes anupper surface defining a rod seat. The saddle is configured to securethe screw head of the bone fastener. The saddle is insertable into thetulip head in a first position with the rod seat offset relative to therod slot. The saddle is rotatable into a second position with the rodseat aligned with the rod slot such that a rod is positionable throughthe rod slot and into the rod seat. The threaded locking cap isthreadable between the two arms of the tulip head to secure the rodtherein.

The assembly may include one or more of the following features. Thesaddle may be twisted or rotated, for example, 90° about a centrallongitudinal axis of the tulip head from the first position to thesecond position. An outer surface of the saddle and the groove may beelliptically shaped, thereby preventing the saddle from rotating out ofalignment. One or more relief cuts in the tulip head may lead into thegroove to allow rotation of the saddle into alignment in a singledirection. The saddle may include a through bore and a pair ofengagement recesses in the upper surface of the saddle on opposite sidesof the through bore. The engagement recesses may be configured tointerface with an assembly tool to facilitate rotation of the saddle.The saddle may include a pair of wings extending outwardly from oppositesides of the saddle. The wings may be receivable in the groove in thetulip head. When the locking cap is threaded downwardly onto the rod,the rod may be pushed against the seat of the saddle, thereby allowingthe saddle to secure the bone fastener. The bore of the tulip head maydefine an internal taper such that the screw head is prevented fromdisengaging from the tulip head by the internal taper. Alternatively,the assembly may include a split ring or clip to secure the bonefastener. The assembly may further include a clamp for accepting thescrew head. When the saddle is in the first position, the clamp is ableto accept the screw head, and when the saddle is in the second position,the bone fastener is locked in position.

According to another embodiment, an orthopedic fixation device includesa tulip head, a locking cap, and a saddle. The tulip head may have twoarms defining a rod slot therebetween. Each of the arms defines athreaded portion along an interior surface. The tulip head has a boreextending therethrough and a groove disposed about the bore. The tuliphead may define a first indicator. The locking cap may have an outerbody defining a thread. The locking cap is threadable between the twoarms of the tulip head to secure a rod therein. The locking cap maydefine a second indicator to show the best alignment to start threadingthe locking cap into the tulip head. The saddle may have an uppersurface defining a rod seat. The saddle is insertable into the tuliphead in an unlocked position with the rod seat offset relative to therod slot, and the saddle is rotatable into a locked position with therod seat aligned with the rod slot such that a rod is positionablethrough the rod slot and into the rod seat.

The device may include one or more of the following features. The firstindicator may include at least one laser mark on an upper surface of oneof the arms. The second indicator may be a groove extending radiallyoutward on a top surface of the locking cap. The device may include athird indicator including a cutout in a side of one of the arms. Thelocking cap may have a first thread at a bottom of the locking cap. Thefirst thread may be broken by a radiused cut, thereby increasing thelikelihood of the thread engaging with the threaded portion of the tuliphead. Starts of the threads of the locking cap and tulip head may betimed when the first indicator and second indicators are aligned,thereby helping to avoid off angle insertion. The thread of the lockingcap may include a top surface angled inward towards a minor diameter anda bottom surface angled outward away from the minor diameter.

According to yet another embodiment, a method of installing anorthopedic fixation device may include one or more of the following: (1)providing a tulip head having two arms defining a rod slot therebetween,the tulip head having a bore extending therethrough and a groovedisposed about the bore; (2) inserting a saddle into the tulip head inan unlocked position, the saddle having an upper surface defining a rodseat, wherein the rod seat is inserted offset relative to the rod slot;and (3) rotating the saddle 90° into a locked position such that the rodseat is aligned with the rod slot and a rod is positionable through therod slot and into the rod seat.

The method may also include one or more of the following: (4) insertinga screw head of a polyaxial bone fastener into the tulip head andsaddle; (5) positioning a rod between the two arms and into the rod slotof the tulip head; and/or (6) threading a locking cap downwardly betweenthe two arms of the tulip head, wherein the rod presses against the rodseat of the saddle, and the saddle presses against the screw head,thereby securing the rod and bone fastener.

Also provided are kits including implants of varying types and sizes,rods, various instruments and tools, and other components for performingthe procedure.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention, and theattendant advantages and features thereof, will be more readilyunderstood by reference to the following detailed description whenconsidered in conjunction with the accompanying drawings, wherein:

FIG. 1 shows a partial perspective view of a tulip head retaining aspinal rod therein and secured by a threaded locking cap according toone embodiment;

FIG. 2 shows a partial perspective view of the tulip head of FIG. 1 withthe threaded locking cap in an upward position with indicators forbeginning to thread the locking cap;

FIG. 3 shows a top view of the locking cap and tulip head withindicators according to one embodiment;

FIG. 4 is a close-up cross-sectional view of the threaded locking capengaged with the tulip head;

FIG. 5 is a top view of the threaded locking cap;

FIG. 6 is a close-up partial perspective view of the bottom of thethreaded locking cap;

FIG. 7 shows a perspective view of the tulip head according to oneembodiment;

FIG. 8 shows a perspective view of a saddle, configured to rotate intoengagement with the tulip head, according to one embodiment;

FIG. 9 shows a partial cross-sectional view of an assembly including asplit ring for applying compression to the screw head according to oneembodiment;

FIG. 10 shows a partial cross-sectional view of an assembly including aclip for retaining the screw head within the tulip head according to oneembodiment;

FIG. 11 is a partial bottom perspective view of the tulip head accordingto one embodiment;

FIG. 12 is a partial bottom perspective view of the tulip head with abone fastener positioned therethrough;

FIG. 13 shows a partial cross-sectional view of the arms of the tuliphead configured to receive the threaded locking cap according to oneembodiment;

FIG. 14 is a perspective view of the tulip head according to oneembodiment;

FIG. 15 is an embodiment of a tulip head with removable reduction tabs;

FIG. 16 shows a partial perspective view of an embodiment of a tulipassembly configured for retaining a uniplanar screw;

FIG. 17 is a partial cross-sectional view of the uniplanar assembly ofFIG. 16;

FIG. 18 shows a partial perspective view of an embodiment of a monoaxialfastener;

FIG. 19 shows a partial cross-sectional view of an embodiment of a tulipassembly with a saddle and clamp for retaining a screw head;

FIG. 20 shows a partial perspective view of a tulip assembly with asaddle in an upward unlocked position according to one embodiment;

FIG. 21 shows a partial perspective view the tulip assembly of FIG. 20with the saddle rotated in a downward locked position;

FIG. 22 shows a perspective view of the saddle according to oneembodiment; and

FIG. 23 shows a perspective view of the tulip head according to oneembodiment.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the disclosure are generally directed to orthopedicdevices, assemblies, implants, systems, and methods for securing aspinal rod during spine surgery. Specifically, embodiments are directedtulip assemblies configured to secure a spinal rod to a bone fastener.Although described with reference to the spine, it will be appreciatedthat the devices and systems described herein may be applied to otherorthopedic locations and applications, such as trauma.

Additional aspects, advantages and/or other features of exampleembodiments of the invention will become apparent in view of thefollowing detailed description. It should be apparent to those skilledin the art that the described embodiments provided herein are merelyexemplary and illustrative and not limiting. Numerous embodiments ormodifications thereof are contemplated as falling within the scope ofthis disclosure and equivalents thereto.

Referring now to FIGS. 1-3, an orthopedic fixation device, implant, orbone fastener assembly 10 is shown according to one embodiment. The bonefastener assembly or implant 10 may include a tulip element or tuliphead 12, a bone fastener 14, and a locking cap 16 for securing a spinalrod 18 in the tulip head 12. For a polyaxial bone fastener 14,tightening the locking cap 16 compresses the rod 18 into the tulip head12, thereby restricting motion of the bone fastener 14 and forming arigid construct.

The tulip head 12 may extend from an upper surface or top 20 to a lowersurface or bottom 22. The tulip head 12 may include a body 24 and arms26 that extend upwardly from the body 24. A central bore 28 may extendthrough the body 24 of the tulip head 12. The opposed arms 26 may definea U-shaped channel or rounded rod slot 30, transverse to the bore 28.The rounded rod slot 30 is sized and configured to accept the rod 18.The rod slot 30 may be oriented perpendicular to the threads 56 of thelocking cap 16. Each of the arms 26 has an interior surface 32 having athreaded portion 34 for engaging the locking cap 16. Each of the arms 26may include an outer surface 36. The outer surface 36 of each of thearms 26 may include one or more tool engagement grooves 38 formed on theouter surface 36 which may be used for holding the tulip head 12 with asuitable tool (not illustrated). The sides of the tulip head 12 maydefine concentric diameters which taper towards the bottom 22 of thetulip head 12. The concentric diameters may have a smaller diameter atthe top 20 of the tulip head 12, or may be a single diameter across thepart. Front and back surfaces 40, 42 of the tulip body 24 may be planaror flat, with an upper flat 44 narrower in width than a lower flat 46.The flats 44, 46 and/or grooves 38 may act as one or morecounter-rotation features when engaged with an instrument.

The rod 18 may be secured in the tulip head 12 with the locking cap 16.The locking cap 16 may include a body with an upper surface 50, a lowersurface 52, and an outer body 54 defining a threaded portion 56. Withemphasis on FIG. 5, the locking cap 16 may be in the form of a set screwwith a drive feature or recess 58 defined in the upper surface 50. Thedrive recess 58 is configured to be engaged by a driving instrument,which is able to insert and tighten the locking cap 16 in the tulip head12. The recess 58 may be a hexalobe, slot, cross, or other suitableshape that may engage with a tool or instrument having a correspondingtip. The recess 58 may extend partway into the body of the locking cap16 or entirely through the locking cap 16. The bottom 52 of the lockingcap 16 may be flat or otherwise configured to ensure consistent contactwith the rod 18. The threaded portion 56 may extend between the upperand lower surfaces 50, 52 or a portion thereof.

As best seen in FIG. 4, the threaded portion 56 of the locking cap 16may have a thread geometry configured to secure the locking cap 16 tothe tulip head 12. The locking cap thread geometry may form a buttresssection with an inward top. For example, a top surface 60 of the lockingcap thread may be angled inward, towards the minor diameter, and abottom surface 62 of the locking cap thread may be angled outward awayfrom the minor diameter. With emphasis on FIG. 6, the first threadbeginning at the bottom 52 of the locking cap 16 may be broken by aradiused cut 64 to increase the strength of the first thread as it isbeing engaged with the tulip head 12 and/or to prevent cross-threadingof the locking cap 16. The locking cap 16 may include a thread geometrythat improves strength, reduces outward splaying forces on the tuliphead 12, increases resistance to cross-threading, allows quickengagement of the locking cap 16, and/or maintains a more consistentinterface with mating instruments. Although a threaded locking cap 16 isexemplified herein, it will be appreciated that a non-threaded cap orother suitable locking cap may be selected to secure the rod 18 and/orthe bone fastener 14.

The tulip head 12 and/or locking cap 16 may include one or moreindicators 70, 72 to show the best alignment to start threading thelocking cap 16 into the tulip head 12, for example, to help avoid offangle insertion. By way of example, each of the indicator(s) 70, 72 mayinclude one or more laser marks, grooves, cutouts, protrusions, or othervisual features configured to align a relative starting position of thelocking cap 16 to the tulip head 12. As best seen in FIG. 3, in oneembodiment, a first indicator 70 may be provided on the tulip head 12.For example, the first indicator 70 may include at least one laser markon the upper surface 20 of one arm 26 of the tulip head 12. The lasermark indicator 70 may include one or more lines (e.g., two parallellines) extending from the inner surface 32 to the outer surface 36 ofone of the arms 26. A second indicator 72 may be provided on the lockingcap 16. For example, the second indicator 72 may include a groove and/orlaser mark on the top surface 50 of the locking cap 16. The secondindicator 72 (e.g., groove and/or laser mark) may also include a groovedefined between one or more lines (e.g., two parallel lines) extendingradially from the recess 58 to the outer surface 54 of the locking cap16. As shown in FIG. 2, a third indicator 38 may be provided on thetulip head 12. The third indicator 38 may include one of the slots orcutouts 38 in the side of one of the arms 26. The slot or cutout 38 maybe aligned with the laser mark indicator 70 on the top 20 of the arm 26.The indicators 70, 72 may help to align the tulip head 12 and lockingcap 16 before threading, in order to help avoid off angle insertion ofthe locking cap 16.

The starts of the threads 34, 56 in the locking cap 16 and tulip head 12may be timed with the corresponding indicators on the locking cap 16and/or tulip head 12. As shown in FIG. 2, when the indicators (e.g.,marking 70, groove 72, and/or cutout 38) are aligned, the start of thethread 54 on the locking cap 16 is close to engaging the thread 34 onthe tulip head 12. The first thread of the threaded portion 56 of thelocking cap 16 may be timed to the indicators on the locking cap 16 andtulip head 12, thereby acting as alignment indicators to allow quickalignment and engagement of the first thread. When the indicators 70, 72are aligned (e.g., the lines of the laser mark 70 are aligned with thegroove 72), the locking cap 16 is able to sit flat and be immediatelyengaged with the tulip head 12. This may help to avoid off angleinsertion of the locking cap 16 into the tulip head 12. The indicators70, 72 may allow the user to quickly and repeatably engage the threads34, 56 of the locking cap 16 with the tulip 12.

The bone fastener 14 may include a bone screw, anchor, clamp, or thelike configured to engage bone. In one embodiment, the bone fastener 14is a bone screw, such as a polyaxial pedicle screw, having a screw head80 and a threaded shaft 82 that extends from the screw head 16. Suitablebone fasteners 14 will be recognized by those of ordinary skill in art.Examples of bone fasteners and other implants and rod constructs aredescribed in more detail, for example, in U.S. Pat. No. 10,368,917,which is incorporated by reference herein in its entirety for allpurposes. It will be appreciated that the threaded shaft 82 may have anumber of different features, such as thread pitch, shaft diameter tothread diameter, overall shaft shape, and the like, depending, forexample, on the particular application. While the screw head 80 may haveany general shape, in the case of a polyaxial fastener 14, at least aportion of the screw head 80 may have a curved surface in order to allowfor rotational movement and/or angular adjustment of the bone fastener14 with respect to the tulip head 12. For example, at least a portion ofthe screw head 80 may be shaped to form a portion of a ball or at leasta portion of a sphere. The screw head 80 may have a tool engagementsurface 84, for example, that can be engaged by a screw-drivinginstrument or other device. In one embodiment, the screw head 80 has ahexalobe recess 84 for driving the screw 14 into bone. It will beappreciated that any suitably shaped tool engagement surface 84 may beprovided. Although a polyaxial bone screw is exemplified herein, it willbe appreciated that the fastener may be substituted with uniplanar,monoaxial, reduction, modular, or other suitable fasteners.

The polyaxial mechanism may be a spherical joint between a sphericalhead 80 of the bone screw 14, the tulip head 12, and a saddle 90. Thesaddle 90, positioned within the bore 28 of the tulip head 12, mayprovide a collar about an upper portion of the screw head 80. Thepolyaxial motion of the bone fastener 14 may be locked when the lockingcap 16 is threaded downwardly, compressing the rod 18 onto the saddle90, which thereby compresses against the spherical head 80 of the bonescrew 14. Thus, the locking cap 16 is able to lock the position of thebone fastener 14 and the rod 18, thereby forming a rigid construct.

In one embodiment shown in FIG. 8, the saddle 90 may include an uppersurface 92, a lower surface 94, an outer surface 96, which may be curvedor rounded, and a bore 98 defined through the saddle 90. A lower portionof the bore 98 may be rounded and sized to receive an upper portion ofthe screw head 80. A rod slot or seat 102 may be defined in the uppersurface 92 of the saddle 90. The rod slot or seat 102 may be configuredto receive a bottom portion of the rod 18 therein. The saddle 90 mayinclude one or more external lips or wings 104. For example, the saddle90 may include two opposed, outwardly extending wings 104 positioned atthe top 92 of the saddle 90.

As shown in FIGS. 9 and 10, the wings 104 may be configured to bereceived in one or more corresponding recesses or grooves 106 in thetulip head 12. The saddle 90 may be rotatable within the tulip head 12in order to engage the saddle 90 within the recesses or grooves 106. Forexample, the saddle 90 may be inserted from the top 20 of the tulip head12 with the seat 102 rotated out of alignment with the rod slot 30 ofthe tulip head 12. After insertion into the tulip head 12, the saddle 90may be rotated about the central longitudinal axis A and into alignmentwith the internal groove 106 in the tulip head 12. In one embodiment,the saddle 90 may be first inserted in a first initial orientation withthe seat 102 at about 90° offset relative to its final position, andthen subsequently rotated 90° to a second final orientation with theseat 102 substantially aligned with the U-shaped rod slot 30 between thearms 26 of the tulip head 12.

A portion of the saddle 90 (e.g., the upper profile of the wings 104)and internal groove 106 of the tulip head 12 may be elliptically shapedto prevent the saddle 90 from inadvertently rotating out of alignment.One or more relief cuts 108 may be provided in the tulip head 12 toallow rotation of the saddle 90 into alignment only in one direction.Thus, the saddle 90 may only be twisted or rotated in a single directionfor engagement with the inner groove 106. One or more grooves orengagement recesses 110 may be cut into the saddle 90 to allow for aninterface with an assembly tool to facilitate rotation of the saddle 90.For example, opposed engagement recesses 110 may be provided within theupper surface 92 on opposite sides of the bore 98, which allows for atool (not shown) to rotate the saddle 90 into position.

With emphasis on FIGS. 9-12, the screw head 80 may be further retainedin the tulip head 12 by a split ring 112, a clip 116, an internal taper120, or other suitable mechanism configured to retain the screw head 80in the body 24 of the tulip 12. In one embodiment shown in FIG. 9, asplit ring 112 may be housed within an internal groove 114 of the tuliphead 12. The split ring 112 may include a ring with a central throughopening and a cut in fluid communication with the central throughopening. The split ring 112 may optionally sit in a corresponding groovein the head 80 of the screw 14. The split ring 112 may apply acompression to the screw head 80, providing a consistent friction to thepolyaxial joint to retain the position of the screw 14.

In one embodiment shown in FIG. 10, the polyaxial mechanism may utilizea clip 116 to retain the screw 14 within the tulip head 12. The clip 116may be received within an internal groove 118 in the tulip head 12. Theclip 116 may be located at a bottom portion of the tulip head 12 beneaththe widest part of the screw head 80. With the clip 116, the sphericalhead 80 of the bone screw 14 may be inserted into the tulip head 12 andthe clip 116 inserted into the internal groove 118 of the tulip head 12to retain the bone screw 14 therein. In this manner, the bone fastener14 is prevented from separating from the tulip head 12.

In one embodiment shown in FIGS. 11-12, the screw head 80 may bepositioned within the bore 28 in the tulip head 12 and prevented fromdisengaging from the tulip head 12 by an internal taper 120 within thetulip head 12. The screw 14 may be inserted from the top 20 of the tuliphead 12 until the screw head 80 contacts the taper 120 at the bottom 22of the tulip head 12. The saddle 90 may be inserted from the top 20 ofthe tulip head 12 and then rotated into alignment with the rod slot 30of the tulip head 12. One or more threads 122 may be cut into the taper120 at the bottom 22 of the tulip head 12. The thread(s) 122 in theinternal taper 120 may be shaped to allow the largest screw possible tothread through the assembly. The tapered tulip reduces the total numberof components and simplifies assembly, but limits the largest screw sizethat may be assembled through the tulip 12.

Turning now to FIGS. 13-14, one or more instrument interfaces may beused for engaging one or more instruments, such as insertion,positioning, reduction, and/or derotation instruments. The instrumentinterfaces may be engaged by instruments, for example, with tabs orgrooves similarly shaped to the reduction features which collapse,pivot, slide, or flex into engagement with the tulip head 12. Forexample, an annular or cylindrical groove 74 may be cut into the outerdiameter of the tulip head 12 for engagement of insertion, reduction,derotation, compression, distraction and/or other holding instruments.The exterior groove 74 may form a single reverse angle groove section.For example, an upward-facing surface 76 of the cylindrical groove 74may be angled outwards away from the central longitudinal axis A of thetulip head 12, while a downward-facing surface 78 of the cylindricalgroove 74 may be angled inwards toward the central axis A. The inwardangle of the downward-facing surface 78 may help to preventdisengagement of the instrument under load by directing forces downwardand towards the central axis A of the tulip head 12.

The locking cap threads 56 may also be engaged with the tulip threads 34to axially constrain the implant 10. The cylindrical groove 74 andthreads 34, 56 allow the central axis A of the implant 10 to beconstrained to the central axis of an instrument. To constrain rotation,one or more slots 38 (e.g., two opposed slots) may be cut into the outerdiameter of the arms 26 which allows engagement of an instrument toprevent rotation. In addition or alternatively, an instrument mayprevent rotation against the upper and lower flats 44, 46. Theinstrument interfaces allow instruments to fully or partially constrainor attach to the implant, provide increased holding strength, decreasesplaying forces which may cause disengagement of instruments, and/orsimplify manufacturing.

Turning now to FIG. 15, the arms 26 of the tulip head 12 may be extendedto provide adjustable length reduction tabs 86. For example, extensionsor extended tabs 86 may be provided to each of the arms 26. The threadedupper portion 34 of the tulip head 12 may be extended along a portion orthe entire extended tabs 86 to allow the rod 18 to be captured andreduced into the tulip head 12 by downwardly threading the locking cap16. The extended tabs 86 may be removable at one or more breaking points88. Each breaking point 88 may be provided as an internal and/orexternal groove, for example, which allows for the extended tabs 86 tobe broken away from the tulip head 12 once they are no longer needed. Inthis embodiment, multiple breaking points 88 may be included at multipleheights to allow the user to break the tabs 86 at a desired height toreduce the amount of turns necessary to turn the locking cap 16 and/orprevent contact with adjacent implants. The reduction tabs 86 may allowfor additional intraoperative adaptability when reducing the rod 18 intothe tulip head 12.

Turning now to FIGS. 16-18, the tulip head 12 may also be applied toother screw designs, such as uniplanar and monoaxial screws. FIGS. 16and 17 show an embodiment of a uniplanar screw assembly 130 (a close-upof the tulip 132 is shown with a portion of the screw shaft omitted forclarity). Similar to the polyaxial screw assembly 10, the uniplanarscrew assembly 130 includes a tulip head 132 and a saddle 90 forretaining a screw head 136 of a uniplanar screw. The uniplanar tulip 132includes a through hole 134 which accepts the screw head 136. For auniplanar screw, the tulip head 12 pivots on the screw head 132 in onlyone direction. The tulip head 12 may be permitted to pivot either alongthe rod slot 30 or perpendicular to the rod slot 30 depending on theorientation of the through hole 134 and screw head 136. Similar to thepolyaxial screw 10, the saddle 90 compresses against the head 136 of thescrew when a threaded locking cap 16 is threaded downwardly onto thespinal rod 18, thereby pushing against the saddle 90. In this lockedposition, the uniplanar screw assembly 130 is locked in place, therebyrestricting motion and locking the position of the uniplanar screw. Aplurality of teeth, groove cuts, or a roughened surface 138 on the screwhead 136 and/or saddle 90 may increase the grip strength of theinterface between the screw head 136 and the bottom of the saddle 90.

FIG. 18 shows an embodiment of a monoaxial screw 140 (a close-up of thetulip 142 is shown with a portion of the screw shaft omitted forclarity). Similar to the polyaxial screw assembly 10, the monoaxialscrew 140 includes a tulip head 142 for receiving a spinal rod 18. Themonoaxial screw 140 combines the tulip head 142 with a bone screw shaft144 into a single unitary component. A threaded locking cap 16 may bethreaded downwardly onto the spinal rod 18, thereby securing the rod 18in the rigid construct. The uniplanar and monoaxial screw designs allowfor rigidity in various directions, which may allow the user to transmitforces to the vertebral body for correction or screw insertion.

Turning now to FIG. 19, an embodiment of a preassembled polyaxialpedicle screw assembly 150 is shown. Similar to the polyaxial screwassembly 10, the polyaxial screw assembly 150 includes a tulip head 152,a saddle 154, and further includes a clamp 156 for retaining the screwhead 80 of the polyaxial screw 14. The saddle 154 is capable oftranslation across a modular bump 158. Similar assemblies are describedin U.S. Pat. No. 10,368,917, which is incorporated by reference hereinin its entirety for all purposes.

With emphasis on FIGS. 20-23, an embodiment of a preassembled polyaxialpedicle screw assembly 160 is shown. Assembly 160 is similar to assembly150 except in this embodiment, assembly of the components is achievedvia rotation and translation of an elliptical saddle 164 into anelliptical bore 192 of the tulip 162 in lieu of the translation of thesaddle 154 across the modular bump 158. This different may ease assemblyduring production and prevent the saddle 164 from inadvertentlytranslating back to an unlocked position.

Similar to implant 10, the polyaxial pedicle screw assembly 160 mayinclude a tulip head 162, a rotatable saddle 164, a bone fastener 14,and a threaded locking cap 16 for securing the spinal rod rod 18 in thetulip head 162. The tulip head 162 may include a body 168 and arms 170that extend upwardly from the body 168. A central bore 172 may extendthrough the body 168 of the tulip head 162. The opposed arms 170 maydefine a U-shaped channel or rod slot 174, transverse to the bore 168.The rounded rod slot 174 is sized and shaped to accept the rod 18perpendicular to the threads of the locking cap 16. Each of the arms 170has an interior surface defining a threaded portion 176 for engaging thethreaded locking cap 16. Each of the arms 170 may include one or moretool engagement surfaces or recesses 178, which may be used for holdingthe tulip head 162 with a suitable tool (not illustrated). Front and/orback surfaces 180 of the tulip body 168 may be flat, for example, toallow for engagement of an instrument to prevent rotation of the tuliphead 162. The rod 18 may be secured in the tulip head 12 with thethreaded locking cap 16.

As shown in FIG. 22, the rotatable saddle 164 may include an uppersurface 182, a lower surface 184, an outer surface 186, which may becurved or rounded, and a bore 188 defined through the saddle 164. Alower portion of the bore 188 may be rounded and sized to receive anupper portion of the clamp 166. A rod slot or seat 190 may be defined inthe upper surface 182 of the saddle 164. The rod slot or seat 190 may beconfigured to receive a bottom portion of the rod 18 therein. The saddle164 may be configured to be received in a recess or bore 192 in thetulip head 162.

The saddle 164 may be rotatable within the tulip head 162 in order toengage the saddle 164 within the internal bore 192. In one embodiment,the outer profile of the saddle 164 and internal bore 192 of the tuliphead 162 may be elliptical in shape, for example, to prevent the saddle164 from rotating out of alignment. As shown in FIG. 20, the saddle 164may be inserted from the top of the tulip head 162 with the seat 190offset about 90° out of alignment with the rod slot 174 of the tuliphead 162. After downward insertion into the tulip head 162, as shown inFIG. 21, the saddle 164 may be twisted or rotated about 90° intoalignment with the internal bore 92 in the tulip head 162. This rotationallows the seat 190 of the saddle 164 to align with the rod slot 174 ofthe tulip head 162 such that the rod 18 may be positioned between thearms 170 of the tulip head 162 and into contact with the seat 190 of thesaddle 164. In this manner, the saddle 164 may be first inserted in afirst initial orientation with the seat 190 at a 90° rotated positionrelative to its final position, and then subsequently rotated 90° to asecond final orientation with the seat 190 aligned with the U-shaped rodslot 174 defined between the arms 170 of the tulip head 162.

One or more grooves or engagement recesses 194 may be cut into thesaddle 164 to allow for an interface with an assembly tool to facilitaterotation of the saddle 164. For example, a pair of opposed engagementrecesses 194 may be provided through the upper surface 182 on oppositesides of the bore 188. The engagement recesses 194 may help to eliminateinterference with the tulip 162 when in the up position, and permitengagement with an assembly tool to rotate the saddle 164. A lead 196 into the ellipse within the tulip 162 may ensure that the saddle 164 isnot damaged during rotation.

In one embodiment, the saddle 164 retains a clamp 166 that accepts thespherical screw head 80, thereby permitting polyaxial motion. The clamp166 may be the same or similar to clamp 156. The clamp 166 may include abody with at least one slit 198 formed therein. The slit 198 may allowfor the clamp 166 to constrict and securely engage the head 80 of thebone screw 14. Outer surfaces of the clamp 166 may abut and engage withthe saddle 164 and/or tulip body 168. Examples of clamps elements aredescribed in more detail, for example, in U.S. Pat. No. 10,368,917,which is incorporated by reference herein in its entirety for allpurposes.

As shown in FIG. 20, when the saddle 164 is in the upward position, theclamp 166 is able to accept the screw head 80. The spherical screw head80 may be inserted into the bottom of the clamp 166. The clamp 166 maybe permitted to expand within the tulip head 162, for example, due tothe one or more slits 198 in the clamp 166. As shown in FIG. 21, thesaddle 164 is then translated down to close clearance within the tuliphead 162, which prevents expansion of the clamp 166 so that thespherical screw head 80 may not be released. The saddle 164 istranslated downward to the elliptical bore 192 of the tulip 162. Then,the saddle 164 is rotated perpendicular to the rod slot 174. Thus, thesaddle 164 is secured by rotation of the saddle 164, for example, by 90°about the central longitudinal axis A of the implant and into engagementwith the elliptical bore 192 within the tulip head 162. Once rotated,the seat 190 of the saddle 164 is properly in alignment with the rodslot 174. The rotatable saddle 164 may allow for ease of assembly andelimination of the complex and tightly toleranced bump. In addition,potential inadvertent release of the saddle 164 to the up position, forexample, due to pressing of the saddle past the bump may also be reducedor eliminated.

The devices and assemblies described herein may allow for improvedfunctionality, strength, and/or ease of manufacturing for pedicle screwhead assemblies. The component features may simplify geometries toreduce profile, increase strength, and/or simplify manufacturing andassembly.

Although the invention has been described in detail and with referenceto specific embodiments, it will be apparent to one skilled in the artthat various changes and modifications can be made without departingfrom the spirit and scope of the invention. Thus, it is intended thatthe invention covers the modifications and variations of this inventionprovided they come within the scope of the appended claims and theirequivalents. It is expressly intended, for example, that all componentsof the various embodiments disclosed above may be combined or modifiedin any suitable configuration.

What is claimed is:
 1. An orthopedic fixation assembly comprising: atulip head having two arms defining a rod slot therebetween, the tuliphead having a bore extending therethrough and a groove disposed aboutthe bore; a bone fastener including a screw head receivable in the tuliphead and a shaft configured for engaging bone; a saddle having an uppersurface defining a rod seat, the saddle configured to secure the screwhead of the bone fastener, wherein the saddle is insertable into thetulip head in a first position and the saddle is rotatable into a secondposition; and a threaded locking cap threadable between the two arms ofthe tulip head to secure the rod therein wherein one or more relief cutsin the tulip head lead into the groove to allow rotation of the saddleinto alignment in a single direction.
 2. The orthopedic fixationassembly of claim 1, wherein the saddle is rotated 90° about a centrallongitudinal axis of the tulip head from the first position to thesecond position.
 3. The orthopedic fixation assembly of claim 1, whereinan outer surface of the saddle and the groove are elliptically shaped,thereby preventing the saddle from rotating out of alignment.
 4. Theorthopedic fixation assembly of claim 1, wherein the saddle includes athrough bore and a pair of engagement recesses in the upper surface ofthe saddle on opposite sides of the through bore, wherein the engagementrecesses are configured to interface with an assembly tool to facilitaterotation of the saddle.
 5. The orthopedic fixation assembly of claim 1,wherein the saddle includes a pair of wings extending outwardly fromopposite sides of the saddle, wherein the wings are receivable in thegroove in the tulip head.
 6. The orthopedic fixation assembly of claim1, wherein when the locking cap is threaded downwardly onto the rod, therod pushes against the seat of the saddle, and the saddle secures thebone fastener.
 7. The orthopedic fixation assembly of claim 1, whereinthe bore of the tulip head defines an internal taper, wherein the screwhead is prevented from disengaging from the tulip head by the internaltaper.
 8. The orthopedic fixation assembly of claim 1, furthercomprising a clamp for accepting the screw head, wherein when the saddleis in the first position, the clamp is able to accept the screw head,and when the saddle is in the second position, the bone fastener islocked in position.
 9. An orthopedic fixation device comprising: a tuliphead having two arms defining a rod slot therebetween, each of the armsdefining a threaded portion along an interior surface, the tulip headhaving a bore extending therethrough and a groove disposed about thebore, wherein the tulip head defines a first indicator; a locking caphaving an outer body defining a thread, wherein the locking cap isthreadable between the two arms of the tulip head to secure a rodtherein, and wherein the locking cap defines a second indicator to showthe best alignment to start threading the locking cap into the tuliphead; and a saddle having an upper surface defining a rod seat, whereinthe saddle is insertable into the tulip head in an unlocked position,and the saddle is rotatable into a locked position, wherein the firstindicator is at least one laser mark on an upper surface of one of thearms.
 10. The orthopedic fixation device of claim 10, wherein the secondindicator is a groove extending radially outward on a top surface of thelocking cap.
 11. The orthopedic fixation device of claim 10, furthercomprising a third indicator including a cutout in a side of one of thearms.
 12. The orthopedic fixation device of claim 10, wherein thelocking cap has a first thread at a bottom of the locking cap, whereinthe first thread is broken by a radiused cut, thereby increasing thelikelihood of the thread engaging with the threaded portion of the tuliphead.
 13. The orthopedic fixation device of claim 10, wherein starts ofthe threads of the locking cap and tulip head are timed when the firstand second indicators are aligned, thereby helping to avoid off angleinsertion.
 14. The orthopedic fixation device of claim 10, wherein thethread of the locking cap includes a top surface angled inward towards aminor diameter and a bottom surface angled outward away from the minordiameter.